Electrochromic multi-layer devices with cross-linked ion conducting polymer

ABSTRACT

Multi-layer electrochromic structures, and processes for assembling such structures, incorporating a cross-linked ion conducting polymer layer that maintains high adhesive and cohesive strength in combination with high ionic conductivity for an extended period of time, the ion conducting polymer layer characterized by electrochemical stability at voltages between about 1.3 V and about 4.4 V relative to lithium, lithium ion conductivity of at least about 10−5 s/cm, and lap shear strength of at least 100 kPa, as measured at 1.27 mm/min in accordance with ASTM International standard D1002 or D3163.

FIELD OF THE INVENTION

The present disclosure generally relates to cross-linked ion conductingpolymers for thin film deposition onto a substrate for the formation ofswitchable electrochromic multi-layer devices, and methods forassembling multi-layer structures comprising such films.

BACKGROUND

Commercial switchable glazing devices, also commonly known as smartwindows and electrochromic window devices, are well known for use asmirrors in motor vehicles, aircraft window assemblies, sunroofs,skylights, and architectural windows. Such devices may comprise, forexample, active inorganic electrochromic layers, organic electrochromiclayers, inorganic ion-conducting layers, organic ion-conducting layersand hybrids of these sandwiched between two conducting layers. When avoltage is applied across these conducting layers the optical propertiesof a layer or layers in between change. Such optical property changestypically include a modulation of the transmissivity of the visible orthe solar sub-portion of the electromagnetic spectrum. For convenience,the two optical states will be referred to as a bleached state and adarkened state in the present disclosure, but it should be understoodthat these are merely examples and relative terms (i.e., a first one ofthe two states is more transmissive or “more bleached” than the otherstate and the other of the two states is less transmissive or “moredarkened” than the first state) and that there could be a set ofbleached and darkened states between the most transmissive state and theleast transmissive state that are attainable for a specificelectrochromic device; for example, it is feasible to switch betweenintermediate bleached and darkened states in such a set.

The broad adoption of electrochromic window devices in the constructionand automotive industries will require a ready supply of low cost,aesthetically appealing, durable products in large area formats.Electrochromic window devices based on metal oxides represent the mostpromising technology for these needs. Typically, such devices comprisetwo electrochromic materials (a cathode and an anode) separated by anion-conducting film and sandwiched between two transparent conductingoxide (TCO) layers. In operation, a voltage is applied across the devicethat causes current to flow in the external circuit, oxidation andreduction of the electrode materials and, to maintain charge balance,mobile cations to enter or leave the electrodes. This facileelectrochemical process causes the window to reversibly change from amore bleached (e.g., a relatively greater optical transmissivity) to amore darkened state (e.g., a relatively lesser optical transmissivity).

Ion conducting materials used in electrochromic windows are typicallycapable of adhering the two TCO layers to one another to form amulti-layer stack. Prior art ion conducting materials, however, sufferfrom certain limitations that impede the performance and durability ofthe electrochromic windows that encompass such ion conducting materials.Specifically, ion conducting polymers having high conductivity to ionssuch as lithium typically do not possess the mechanical propertiesnecessary to endure physical stresses and strain placed on themulti-layer stack during its manufacture, its incorporation into astructure (e.g., an automobile, aircraft, or building), and/or itsintended end-use environment (e.g., as an architectural window, sunroof,skylight, mirror, etc., in such a structure). Conversely, ion conductingmaterials capable of enduring significant physical stress withoutsuccumbing to adhesive or cohesive failure typically do not possess theelectrochemical properties necessary to maintain high ionic conductivityover an extended period of time under variable environmental conditions.

Briefly, therefore, the present disclosure is directed to multi-layerelectrochromic structures incorporating a cross-linked ion conductingpolymer layer that maintains high adhesive and cohesive strength incombination with high ionic conductivity for an extended period of time.

One aspect of the present disclosure is an electrochromic structurecomprising a cross-linked lithium-ion conducting polymer layer betweenopposing first and second substrates, the first substrate comprising afirst electrochromic layer between the first substrate and thecross-linked lithium-ion conducting polymer layer, wherein, at roomtemperature, the cross-linked ion conducting polymer (i) iselectrochemically stable at voltages between about 1.3 V and about 4.4 Vrelative to lithium, (ii) has a lithium ion conductivity of at leastabout 10⁻⁵ S/cm, and (iii) lap shear strength of at least 100 kPa, asmeasured at 1.27 mm/min at room temperature in accordance with ASTMInternational standard D1002 or D3163.

A further aspect of the present disclosure is a process for forming anelectrochromic structure. The process of assembling an electrochromicmulti-layer stack comprises (A) depositing a layer of an ion conductingpolymer feedstock onto a first multi-layer stack, the first multi-layerstack comprising a first substrate and a first electrode layer, (B)laminating a second multi-layer stack comprising a second substrate anda second electrode layer to the first multi-layer stack to form anelectrochromic multi-layer stack comprising, in succession, the firstsubstrate, the first electrode layer, the ion conducting polymerfeedstock layer, the second electrode layer, and the second substrate,the first electrode layer, the second electrode layer, or bothcomprising an electrochromic material; and (C) irradiating theelectrochromic multi-layer stack to polymerize the ion conductingpolymer feedstock, forming a cross-linked ion conducting polymer layer,wherein the cross-linked ion conducting polymer, at room temperature,(i) is electrochemically stable at voltages between about 1.3 V andabout 4.4 V relative to lithium, (ii) has a lithium ion conductivity ofat least about 10⁻⁵ S/cm, and (iii) lap shear strength of at least 100kPa, as measured at 1.27 mm/min in accordance with ASTM Internationalstandard D1002 or D3163.

A further aspect of the present disclosure is an ion conducting polymerfeedstock material having a viscosity of about 20,000 cP to about 50,000cP, the ion conducting polymer feedstock material comprising betweenabout 5 wt. % and about 50 wt. % monomer, oligomer, or a mixture ofmonomers and/or oligomers, an ionizable charge carrier, and aplasticizer. In one embodiment, the ion conducting polymer feedstockmaterial is capable of being cross-linked to form a cross-linked ionconducting polymer, wherein the cross-linked ion conducting polymer atroom temperature is characterized by (i) electrochemical stability atvoltages between about 1.3 V and about 4.4 V, (ii) ionic conductivity ofat least about 10⁻⁵ S/cm, and (iii) lap shear strength of at least 100kPa, as measured at 1.27 mm/min in accordance with ASTM Internationalstandard D1002 or D3163.

Other objects and features will be described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-section of a multi-layer electrochromicdevice of the present disclosure.

FIG. 2 is a plot illustrating variation in lap shear strength withpolymer content.

FIG. 3 is a stress-strain curve corresponding to a lap shear strengthmeasurement, as more fully described in Example 3.

FIG. 4 is an embodiment of a cross-section of a device duringmanufacturing.

Corresponding reference characters indicate corresponding partsthroughout the drawings. Additionally, relative thicknesses of thelayers in the different figures do not represent the true relationshipin dimensions. For example, the substrates are typically much thickerthan the other layers. The figures are drawn only for the purpose toillustrate connection principles, not to give any dimensionalinformation.

ABBREVIATIONS AND DEFINITIONS

The following definitions and methods are provided to better define thepresent disclosure and to guide those of ordinary skill in the art inthe practice of the present disclosure. Unless otherwise noted, termsare to be understood according to conventional usage by those ofordinary skill in the relevant art.

The terms “amine” or “amino,” as used herein alone or as part of anothergroup, represents a group of formula —N(R⁸)(R⁹), wherein R⁸ and R⁹ areindependently hydrogen, hydrocarbyl, substituted hydrocarbyl, silyl, orR⁸ and R⁹ taken together form a substituted or unsubstituted cyclic orpolycyclic moiety, each as defined in connection with such terms,typically having from 3 to 8 atoms in the ring. “Substituted amine,” forexample, refers to a group of formula —N(R⁸)(R⁹), wherein at least oneof R⁸ and R⁹ are other than hydrogen. “Unsubstituted amine,” forexample, refers to a group of formula —N(R⁸)(R⁹), wherein R⁸ and R⁹ areboth hydrogen.

The term “anodic electrochromic material” refers to an electrochromicmaterial that changes from a less optically transmissive state to a lessoptically transmissive state (e.g., darkens) upon oxidation (i.e.,removal of electrons).

The term “aryl” as used herein alone or as part of another group denotesoptionally substituted homocyclic aromatic groups, preferably monocyclicor bicyclic groups containing from 6 to 12 carbons in the ring portion,such as phenyl, biphenyl, naphthyl, substituted phenyl, substitutedbiphenyl or substituted naphthyl. Phenyl and substituted phenyl are themore preferred aryl.

The term “bleach” refers to the transition of an electrochromic materialfrom a first optical state to a second optical state wherein the firstoptical state is less transmissive than the second optical state.

The term “bleached state voltage” refers to the open circuit voltage(V^(oc)) of the anodic electrochromic layer versus Li/Li+ in anelectrochemical cell in a propylene carbonate solution containing 1Mlithium perchlorate when the transmissivity of said layer is at 95% ofits “fully bleached state” transmissivity.

The term “cathodic electrochromic material” refers to an electrochromicmaterial that changes from a less optically transmissive state to a moreoptically transmissive state (e.g., darkens) upon reduction (i.e.,addition of electrons).

The term “darken” refers to the transition of an electrochromic materialfrom a first optical state to a second optical state wherein the firstoptical state is more transmissive than the second optical state.

The term “electrochromic material” refers to a material that is able tochange its optical properties as a result of the insertion or extractionof ions and electrons. For example, an electrochromic material maychange between (i) a colored, translucent or opaque state and atransparent state or (ii) a colored, opaque state and a colored,translucent state. In some examples, the change can be reversible whilein other examples, the change can be irreversible.

The term “electrical potential,” or simply “potential,” refers to thevoltage occurring across a device comprising an electrode/ionconductor/electrode stack .

The term “electrochemically matched” refers to a set of cathode andanode electrochromic films or materials with similar charge capacitiesand complementary oxidation states such that when joined together by asuitable ion-conducting and electrically insulating layer, a functionalelectrochromic device is formed that shows reversible switching behaviorover a substantial range of the theoretical charge capacities of thefilms or materials, respectively.

The term “electrode layer” refers to a layer capable of conducting ionsas well as electrons. The electrode layer contains a species that can beoxidized when ions are inserted into the material and contains a speciesthat can be reduced when ions are extracted from the layer. This changein oxidation state of a species in the electrode layer is responsiblefor the change in optical properties in the device.

The terms “first,” “second,” “third,” “fourth,” and the like in thedescription and in the claims, if any, are used for distinguishingbetween similar elements and not necessarily for describing a particularsequential or chronological order. It is to be understood that the termsso used are interchangeable under appropriate circumstances such thatthe embodiments described herein are, for example, capable of operationin sequences other than those illustrated or otherwise described herein.Furthermore, the terms “include,” and “have,” and any variationsthereof, are intended to cover a non-exclusive inclusion, such that anactivity, process, method, system, article, device, or apparatus thatcomprises a list of elements is not necessarily limited to thoseelements, but may include other elements not expressly listed orinherent to such activity, process, method, system, article, device, orapparatus.

The term “fully bleached state” as used in connection with an anodicelectrochromic material refers to the state of maximum transmissivity ofan anodic electrochromic layer in an electrochemical cell at or above1.5V versus Li/Li+ in a propylene carbonate solution containing 1 Mlithium perchlorate at 25° C. (under anhydrous conditions and in an Aratmosphere).

The terms “halide,” “halogen” or “halo” as used herein alone or as partof another group refer to chlorine, bromine, fluorine, and iodine.

The term “lap shear strength” as used herein refers to the stress pointat which either adhesive or cohesive failure occurs.

The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,”“under,” and the like in the description and in the claims, if any, areused for descriptive purposes and not necessarily for describingpermanent relative positions. It is to be understood that the terms soused are interchangeable under appropriate circumstances such that theembodiments of the disclosure described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

The term “silyl” as used herein describes substituents of the generalformula —Si(X⁸)(X⁹)(X¹⁰) where X⁸, X⁹, and X¹⁰ are independentlyhydrocarbyl or substituted hydrocarbyl.

The “substituted hydrocarbyl” moieties described herein are hydrocarbylmoieties which are substituted with at least one atom other than carbon,including moieties in which a carbon chain atom is substituted with ahetero atom such as nitrogen, oxygen, silicon, phosphorous, boron,sulfur, or a halogen atom. These substituents include halogen,heterocyclo, alkoxy, alkenoxy, alkynoxy, aryloxy, hydroxy, protectedhydroxy, keto, acyl, acyloxy, nitro, amino, amido, nitro, cyano, thiol,ketals, acetals, esters, ethers, and thioethers.

The term “transmissive” is used to denote transmission ofelectromagnetic radiation through a material.

The term “transmissivity” refers to the fraction of light transmittedthrough an electrochromic film. Unless otherwise stated, thetransmissivity of an electrochromic film is represented by the numberT_(vis). T_(vis) is calculated/obtained by integrating the transmissionspectrum in the wavelength range of 400-730 nm using the spectralphotopic efficiency I_p(lambda) (CIE, 1924) as a weighting factor. (Ref:ASTM E1423).

The term “transparent” is used to denote substantial transmission ofelectromagnetic radiation through a material such that, for example,bodies situated beyond or behind the material can be distinctly seen orimaged using appropriate image sensing technology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To address these deficiencies, the present disclosure provides ionconducting polymers with sufficient cross-link densities to endure highlevels of physical stress without limiting ion mobility, while remainingelectrochemically stable.

FIG. 1 depicts a cross-sectional structural diagram of electrochromicdevice 1 according to a first embodiment of the present disclosure.Moving outward from the center, electrochromic device 1 comprises an ionconductor layer 10. First electrode layer 20 is on one side of and incontact with a first surface of ion conductor layer 10, and secondelectrode layer 21 is on the other side of and in contact with a secondsurface of ion conductor layer 10. In addition, at least one of firstand second electrode layers 20, 21 comprises electrochromic material; inone embodiment, first and second electrode layers 20, 21 each compriseelectrochromic material. The central structure, that is, layers 20, 10,21, is positioned between first and second electrically conductivelayers 22 and 23 which, in turn, are arranged against outer substrates24, 25. Elements 22, 20, 10, 21, and 23 are collectively referred to asan electrochromic stack 28.

Electrically conductive layer 22 is in electrical contact with oneterminal of a power supply (not shown) via bus bar 26 and electricallyconductive layer 23 is in electrical contact with the other terminal ofa power supply (not shown) via bus bar 27 whereby the transmissivity ofelectrochromic device 10 may be changed by applying a voltage pulse toelectrically conductive layers 22 and 23. The pulse causes electrons andions to move between first and second electrode layers 20 and 21 and, asa result, electrochromic material in the first and/or second electrodelayer(s) change(s) optical states, thereby switching electrochromicdevice 1 from a more transmissive state to a less transmissive state, orfrom a less transmissive state to a more transmissive state. In oneembodiment, electrochromic device 1 is transparent before the voltagepulse and less transmissive (e.g., more reflective or colored) after thevoltage pulse or vice versa.

It should be understood that the reference to a transition between aless transmissive and a more transmissive state is non-limiting and isintended to describe the entire range of transitions attainable byelectrochromic materials to the transmissivity of electromagneticradiation. For example, the change in transmissivity may be a changefrom a first optical state to a second optical state that is (i)relatively more absorptive (i.e., less transmissive) than the firststate, (ii) relatively less absorptive (i.e., more transmissive) thanthe first state, (iii) relatively more reflective (i.e., lesstransmissive) than the first state, (iv) relatively less reflective(i.e., more transmissive) than the first state, (v) relatively morereflective and more absorptive (i.e., less transmissive) than the firststate or (vi) relatively less reflective and less absorptive (i.e., moretransmissive) than the first state. Additionally, the change may bebetween the two extreme optical states attainable by an electrochromicdevice, e.g., between a first transparent state and a second state, thesecond state being opaque or reflective (mirror). Alternatively, thechange may be between two optical states, at least one of which isintermediate along the spectrum between the two extreme states (e.g.,transparent and opaque or transparent and mirror) attainable for aspecific electrochromic device. Unless otherwise specified herein,whenever reference is made to a less transmissive and a moretransmissive, or even a bleached-colored transition, the correspondingdevice or process encompasses other optical state transitions such asnon-reflective-reflective, transparent-opaque, etc. Further, the term“bleached” refers to an optically neutral state, e.g., uncolored,transparent or translucent. Still further, unless specified otherwiseherein, the “color” of an electrochromic transition is not limited toany particular wavelength or range of wavelengths. As understood bythose of skill in the art, the choice of appropriate electrochromic andcounter electrode materials governs the relevant optical transition.

In general, the change in transmissivity preferably comprises a changein transmissivity to electromagnetic radiation having a wavelength inthe range of infrared to ultraviolet radiation. For example, in oneembodiment the change in transmissivity is predominately a change intransmissivity to electromagnetic radiation in the infrared spectrum. Ina second embodiment, the change in transmissivity is to electromagneticradiation having wavelengths predominately in the visible spectrum. In athird embodiment, the change in transmissivity is to electromagneticradiation having wavelengths predominately in the ultraviolet spectrum.In a fourth embodiment, the change in transmissivity is toelectromagnetic radiation having wavelengths predominately in theultraviolet and visible spectra. In a fifth embodiment, the change intransmissivity is to electromagnetic radiation having wavelengthspredominately in the infrared and visible spectra. In a sixthembodiment, the change in transmissivity is to electromagnetic radiationhaving wavelengths predominately in the ultraviolet, visible andinfrared spectra.

Referring again to FIG. 1, the materials making up electrochromic stack28 may comprise organic or inorganic materials, and they may be solid orliquid. For example, in certain embodiments the electrochromic stack 28comprises materials that are inorganic, solid (i.e., in the solidstate), or both inorganic and solid. Inorganic materials have shownbetter reliability in architectural applications. Materials in the solidstate can also offer the advantage of not having containment and leakageissues, as materials in the liquid state often do. It should beunderstood that any one or more of the layers in the stack may containsome amount of organic material, but in many implementations one or moreof the layers contains little or no organic matter. The same can be saidfor liquids that may be present in one or more layers in small amounts.In certain other embodiments some or all of the materials making upelectrochromic stack 28 are organic. Organic ion conductors can offerhigher mobilities and thus potentially better device switchingperformance. Organic electrochromic layers can provide higher contrastratios and more diverse color options. Each of the layers in theelectrochromic device is discussed in detail, below. It should also beunderstood that solid state material may be deposited or otherwiseformed by processes employing liquid components such as certainprocesses employing sol-gels or chemical vapor deposition.

Ion conductor layer 10 serves as a medium through which ions aretransported (in the manner of an electrolyte) when the electrochromicdevice switches between an optically less transmissive (“colored”) stateand an optically more transmissive (“bleached”). Stated differently, theion conducting layer permits sufficient ionic conduction between thefirst and second electrode layers 20, 21 upon the application of avoltage across electrochromic stack 28. Depending on the choice ofmaterials, such ions include lithium ions (Li⁺) and hydrogen ions (H⁺)(i.e., protons). Other ions may also be employed in certain embodiments.These include deuterium ions (D⁺), sodium ions (Na⁺), potassium ions(K⁺), calcium ions (Ca⁺⁺), barium ions (Ba⁺⁺), strontium ions (Sr⁺⁺),and magnesium ions (Mg⁺⁺). In one embodiment, ion conductor layer 10 hasa lithium ion conductivity of at least about 10⁻⁵ S/cm at roomtemperature (i.e., 25° C.). For example, in one such embodiment, ionconductor layer 10 has a lithium ion conductivity of at least about 10⁻⁴S/cm at room temperature. By way of further example, in one suchembodiment ion conductor layer 10 has a lithium ion conductivity of atleast about 10⁻³ S/cm at room temperature. By way of further example, inone such embodiment ion conductor layer 10 has a lithium ionconductivity of at least about 10⁻² S/cm at room temperature.Preferably, ion conductor layer 10 has sufficiently low electronconductivity that negligible electron transfer takes place during normaloperation.

Ion conductor layer 10 is also preferably sufficiently durable so as towithstand repeated cycling of the electrochromic device between anoptically less transmissive state and an optically more transmissivestate. For example, in one such embodiment, lithium ion conductivity ofion conductor layer 10 varies less than about 0.1% to about 5% uponcycling of the electrochromic device between a less transmissive state(e.g. about 5% transmissive) and a more transmissive state (e.g. about70% transmissive) for at least 100 hours at 85° C. By way of furtherexample, in one such embodiment lithium ion conductivity of ionconductor layer 10 varies less than about 0.01% to about 2% upon cyclingof the electrochromic device between a less transmissive state and amore transmissive state for at least 100 hours at 85° C.

In some embodiments, ion conductor layer 10 has a relatively low glasstransition temperature (T_(g)), enabling the cured polymer network toremain soft and pliable upon exposure of electrochromic stack 28 to lowenvironmental temperatures. For example, in one embodiment, ionconductor layer 10 has a glass transition temperature of less than about−5° C. to about −40° C. and more particularly between the range of about−10° C. to about −25° C. The glass transition temperature of ionconductor layer 10 may be lowered under controlled conditions, e.g. theaddition of a plasticizer, according to methods known in the art (see,e.g., U.S. Patent Publication No. 20120237704).

The voltage applied across electrochromic stack 28 to reversibly switchelectrochromic device between an optically less transmissive state andan optically more transmissive state is typically in the range of about1 V to about ˜4.5 V versus lithium (Li/Li⁺). In general, therefore, itis preferred that ion conducting layer be electrochemically stable (orwithin the electrochemical window) at voltages within this range. Forexample, in one such embodiment the ion conducting layer iselectrochemically stable at voltages in the range of about 1.3 V andabout 4.4 V relative to lithium (Li/Li⁺). By way of further example, inone such embodiment the ion conducting layer is electrochemically stableat voltages in the range of about 1.3 V and about 4 V relative tolithium (Li/Li⁺). By way of further example, in one such embodiment theion conducting layer is electrochemically stable at voltages in therange of about 2 V and about 4 V relative to lithium (Li/Li⁺).

Additionally, to enable electrochromic stack 28 to endure a range ofphysical stresses to which it may be exposed during the manufacture ofelectrochromic device 1, its incorporation into a structure (e.g., anautomobile, aircraft, or building), and/or its intended end-useenvironment (e.g., as an architectural window, sunroof, skylight,mirror, etc., in such a structure), ion conductor layer 10 alsopossesses sufficient cohesion and adhesion to the first and secondelectrode layers 20 and 21. For example, in one embodiment, ionconductor layer 10 has a lap shear strength of at least 100 kPa to atleast 600 kPa, and more particularly between the range of 200 kPa to 400kPa, as measured at 1.27 mm/min, at room temperature, in accordance withASTM International standard D1002 or D3163. Preferably, ion conductorlayer 10 is elastically deformable. In one exemplary embodiment, ionconductor layer 10 has an elongation to failure of at least 1 mm.

Some non-exclusive examples of electrolytes typically incorporated intoion conductor layer 10 are: solid polymer electrolytes (SPE), such aspoly(ethylene oxide) with a dissolved lithium salt; gel polymerelectrolytes (GPE), such as mixtures of poly(methyl methacrylate) andpropylene carbonate with a lithium salt; composite gel polymerelectrolytes (CGPE) that are similar to GPE's but with an addition of asecond polymer such a poly(ethylene oxide), and liquid electrolytes (LE)such as a solvent mixture of ethylene carbonate/diethyl carbonate with alithium salt; and composite organic-inorganic electrolytes (CE),comprising an LE with an addition of titania, silica or other oxides.Some non-exclusive examples of lithium salts used are LiTFSI (lithiumbis(trifluoromethane) sulfonimide), LiBF₄ (lithium tetrafluoroborate),LiAsF₆ (lithium hexafluoro arsenate), LiCF₃SO₃ (lithium trifluoromethanesulfonate), and LiClO₄ (lithium perchlorate). Additional examples ofsuitable ion conducting layers include silicates, silicon oxides,tungsten oxides, tantalum oxides, niobium oxides, and borates. Thesilicon oxides include silicon-aluminum-oxide. These materials may bedoped with different dopants, including lithium. Lithium doped siliconoxides include lithium silicon-aluminum-oxide. In some embodiments, theion conducting layer comprises a silicate-based structure. In otherembodiments, suitable ion conductors particularly adapted for lithiumion transport include, but are not limited to, lithium silicate, lithiumaluminum silicate, lithium aluminum borate, lithium aluminum fluoride,lithium borate, lithium nitride, lithium zirconium silicate, lithiumniobate, lithium borosilicate, lithium phosphosilicate, and other suchlithium-based ceramic materials, silicas, or silicon oxides, includinglithium silicon-oxide.

The thickness of the ion conductor layer 10 will vary depending on thematerial. In some embodiments using an inorganic ion conductor the ionconductor layer 10 is about 250 nm to 1 nm thick, and more particularlyabout 50 nm to 5 nm thick. In some embodiments using an organic ionconductor, the ion conducting layer is between about 1 μm and 1000 μmthick or, more particularly, between about 100 μm and 500 μm thick. Thethickness of the ion conducting layer is also substantially uniform. Inone embodiment, a substantially uniform ion conducting layer varies bynot more than about +/−10% in each of the aforementioned thicknessranges. In another embodiment, a substantially uniform ion conductinglayer varies by not more than about +/−5% in each of the aforementionedthickness ranges. In another embodiment, a substantially uniform ionconducting layer varies by not more than about +/−3% in each of theaforementioned thickness ranges.

Still referring to FIG. 1, the power supply (not shown) connected to busbars 26, 27 is typically a voltage source with optional current limitsor current control features and may be configured to operate inconjunction with local thermal, photosensitive or other environmentalsensors. The voltage source may also be configured to interface with anenergy management system, such as a computer system that controls theelectrochromic device according to factors such as the time of year,time of day, and measured environmental conditions. Such an energymanagement system, in conjunction with large area electrochromic devices(e.g., an electrochromic architectural window), can dramatically lowerthe energy consumption of a building.

At least one of the substrates 24, 25 is preferably transparent, inorder to reveal the electrochromic properties of the stack 28 to thesurroundings. Any material having suitable optical, electrical, thermal,and mechanical properties may be used as first substrate 24 or secondsubstrate 25. Such substrates include, for example, glass, plastic,metal, and metal coated glass or plastic. Non-exclusive examples ofpossible plastic substrates are polycarbonates, polyacrylics,polyurethanes, urethane carbonate copolymers, polysulfones, polyimides,polyacrylates, polyethers, polyester, polyethylenes, polyalkenes,polyimides, polysulfides, polyvinylacetates and cellulose-basedpolymers. If a plastic substrate is used, it may be barrier protectedand abrasion protected using a hard coat of, for example, a diamond-likeprotection coating, a silica/silicone anti-abrasion coating, or thelike, such as is well known in the plastic glazing art. Suitable glassesinclude either clear or tinted soda lime glass, including soda limefloat glass. The glass may be tempered or untempered. In someembodiments of electrochromic device 1 with glass, e.g. soda lime glass,used as first substrate 24 and/or second substrate 25, there is a sodiumdiffusion barrier layer (not shown) between first substrate 24 and firstelectrically conductive layer 22 and/or between second substrate 25 andsecond electrically conductive layer 23 to prevent the diffusion ofsodium ions from the glass into first and/or second electricallyconductive layer 23. In some embodiments, second substrate 25 isomitted.

The substrate first and or second substrates may also be a composite oftwo or materials. Thin glass or plastic substrates may be used tomanufacture the electrochromic device and may be laminated to a thickercarrier glass to provide mechanical strength and durability to largescale products incorporating the electrochromic devices. In someembodiments the carrier glass is tempered glass. The thicker carrierglass may be laminated to the thinner substrates prior to deposition ofthe layers of the electrochromic device or after the completion of thedevice and the lamination of the ion conductor. Additionally there maybe more than one electrochromic device formed on thin glass or plasticlaminated to carrier glass, thereby increasing the possible strain onthe device. The use of carrier glass increases the weight andembodiments of the current invention may be advantageous in maintainingthe durability and mechanical strength of devices according toembodiments of this disclosure. The tunability of the ion conductor toprovide the desired bonding strength once cross-linked is an advantagein these embodiments.

Additionally, in an Insulated Glass Unit (IGU) there are typically atleast two complete electrochromic devices integrated on each of thepanes. In some embodiments there may be more than two panes havingelectrochromic devices or an additional pane of glass only to increasethe insulative properties of the IGU.

In one preferred embodiment of the disclosure, first substrate 24 andsecond substrate 25 are each float glass. In certain embodiments forarchitectural applications, this glass is at least 0.5 meters by 0.5meters, and can be much larger, e.g., as large as about 3 meters by 4meters. In such applications, this glass is typically at least about 2mm thick and more commonly 4-6 mm thick.

Independent of application, the electrochromic devices of the presentdisclosure may have a wide range of sizes. In general, it is preferredthat the electrochromic device comprise a substrate having a surfacewith a surface area of at least 0.001 meter². For example, in certainembodiments, the electrochromic device comprises a substrate having asurface with a surface area of at least 0.01 meter². By way of furtherexample, in certain embodiments, the electrochromic device comprises asubstrate having a surface with a surface area of at least 0.1 meter².By way of further example, in certain embodiments, the electrochromicdevice comprises a substrate having a surface with a surface area of atleast 1 meter². By way of further example, in certain embodiments, theelectrochromic device comprises a substrate having a surface with asurface area of at least 5 meter². By way of further example, in certainembodiments, the electrochromic device comprises a substrate having asurface with a surface area of at least 10 meter².

At least one of the two electrically conductive layers 22, 23 is alsopreferably transparent in order to reveal the electrochromic propertiesof the stack 28 to the surroundings. In one embodiment, electricallyconductive layer 23 is transparent. In another embodiment, electricallyconductive layer 22 is transparent. In another embodiment, electricallyconductive layers 22, 23 are each transparent. In certain embodiments,one or both of the electrically conductive layers 22, 23 is inorganicand/or solid. Electrically conductive layers 22 and 23 may be made froma number of different transparent materials, including transparentconductive oxides, thin metallic coatings, networks of conductive nanoparticles (e.g., rods, tubes, dots) conductive metal nitrides, andcomposite conductors. Transparent conductive oxides include metal oxidesand metal oxides doped with one or more metals. Examples of such metaloxides and doped metal oxides include indium oxide, indium tin oxide,doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminumzinc oxide, doped zinc oxide, ruthenium oxide, doped ruthenium oxide andthe like. Transparent conductive oxides are sometimes referred to as(TCO) layers. Thin metallic coatings that are substantially transparentmay also be used. Examples of metals used for such thin metalliccoatings include gold, platinum, silver, aluminum, nickel, and alloys ofthese. Examples of transparent conductive nitrides include titaniumnitrides, tantalum nitrides, titanium oxynitrides, and tantalumoxynitrides. Electrically conducting layers 22 and 23 may also betransparent composite conductors. Such composite conductors may befabricated by placing highly conductive ceramic and metal wires orconductive layer patterns on one of the faces of the substrate and thenover-coating with transparent conductive materials such as doped tinoxides or indium tin oxide. Ideally, such wires should be thin enough asto be invisible to the naked eye (e.g., about 100 μm or thinner).Non-exclusive examples of electron conductors 22 and 23 transparent tovisible light are thin films of indium tin oxide (ITO), tin oxide, zincoxide, titanium oxide, n- or p-doped zinc oxide and zinc oxyfluoride.Metal-based layers, such as ZnS/Ag/ZnS and carbon nanotube layers havebeen recently explored as well. Depending on the particular application,one or both electrically conductive layers 22 and 23 may be made of orinclude a metal grid.

The thickness of the electrically conductive layer may be influenced bythe composition of the material comprised within the layer and itstransparent character. In some embodiments, electrically conductivelayers 22 and 23 are transparent and each have a thickness that isbetween about 1000 nm and about 50 nm. In some embodiments, thethickness of electrically conductive layers 22 and 23 is between about500 nm and about 100 nm. In other embodiments, the electricallyconductive layers 22 and 23 each have a thickness that is between about400 nm and about 200 nm. In general, thicker or thinner layers may beemployed so long as they provide the necessary electrical properties(e.g., conductivity) and optical properties (e.g., transmittance). Forcertain applications it will generally be preferred that electricallyconductive layers 22 and 23 be as thin as possible to increasetransparency and to reduce cost.

Referring again to FIG. 1, the function of the electrically conductivelayers is to apply the electric potential provided by a power supplyover the entire surface of the electrochromic stack 28 to interiorregions of the stack. The electric potential is transferred to theconductive layers though electrical connections to the conductivelayers. In some embodiments, bus bars, one in contact with firstelectrically conductive layer 22 and one in contact with secondelectrically conductive layer 23 provide the electric connection betweenthe voltage source and the electrically conductive layers 22 and 23.

In one embodiment, the sheet resistance, Rs, of the first and secondelectrically conductive layers 22 and 23 is about 500 Ω/□ to 1 Ω/□. Insome embodiments, the sheet resistance of first and second electricallyconductive layers 22 and 23 is about 100 Ω/□ to 5 Ω/□. In general, it isdesirable that the sheet resistance of each of the first and secondelectrically conductive layers 22 and 23 be about the same. In oneembodiment, first and second electrically conductive layers 22 and 23each have a sheet resistance of about 20 Ω/□ to about 8 Ω/□.

To facilitate more rapid switching of electrochromic device 1 from astate of relatively greater transmittance to a state of relativelylesser transmittance, or vice versa, at least one of electricallyconductive layers 22, 23 preferably has a sheet resistance, R_(s), tothe flow of electrons through the layer that is non-uniform. Forexample, in one embodiment only one of first and second electricallyconductive layers 22, 23 has a non-uniform sheet resistance to the flowof electrons through the layer. Alternatively, and typically morepreferably, first electrically conductive layer 22 and secondelectrically conductive layer 23 each have a non-uniform sheetresistance to the flow of electrons through the respective layers.Without being bound by any particular theory, it is presently believedthat spatially varying the sheet resistance of electrically conductivelayer 22, spatially varying the sheet resistance of electricallyconductive layer 23, or spatially varying the sheet resistance ofelectrically conductive layer 22 and electrically conductive layer 23improves the switching performance of the device by controlling thevoltage drop in the conductive layer to provide uniform potential dropor a desired non-uniform potential drop across the device, over the areaof the device.

In general, electrical circuit modeling may be used to determine thesheet resistance distribution providing desired switching performance,taking into account the type of electrochromic device, the device shapeand dimensions, electrode characteristics, and the placement ofelectrical connections (e.g., bus bars) to the voltage source. The sheetresistance distribution, in turn, can be controlled, at least in part,by grading the thickness of the first and/or second electricallyconductive layer(s), grading the composition of the first and/or secondelectrically conductive layer(s), or patterning the first and/or secondelectrically conductive layer(s), or some combination of these.

In one exemplary embodiment, the electrochromic device is a rectangularelectrochromic window. Referring again to FIG. 1, in this embodimentfirst substrate 24 and second substrate 25 are rectangular panes ofglass or other transparent substrate and electrochromic device 1 has twobus bars 26, 27 located on opposite sides of first electrode layer 20and second electrode layer 21, respectively. When configured in thismanner, it is generally preferred that the resistance to the flow ofelectrons in first electrically conductive layer 22 increases withincreasing distance from bus bar 26 and that the resistance to the flowof electrons in second electrically conductive layer 23 increases withincreasing distance from bus bar 27. This, in turn, can be effected, forexample, by decreasing the thickness of first electrically conductivelayer 22 as a function of increasing distance from bus bar 26 anddecreasing the thickness of second electrically conductive layer 23 as afunction of increasing distance from bus bar 27.

The multi-layer devices of the present disclosure may have a shape otherthan rectangular, may have more than two bus bars, and/or may not havethe bus bars on opposite sides of the device. For example, themulti-layer device may have a perimeter that is more generally aquadrilateral, or a shape with greater or fewer sides than four forexample, the multi-layer device may be triangular, pentagonal,hexagonal, etc., in shape. By way of further example, the multi-layerdevice may have a perimeter that is curved but lacks vertices, e.g.,circular, oval, etc. By way of further example, the multi-layer devicemay comprise three, four or more bus bars connecting the multi-layerdevice to a voltage source, or the bus bars, independent of number maybe located on non-opposing sides. In each of such instances, thepreferred resistance profile in the electrically conductive layer(s) mayvary from that which is described for the rectangular, two bus barconfiguration.

Referring again to FIG. 1, at least one of first and second electrodelayers 20 and 21 is electrochromic, one of the first and secondelectrode layers is the counter electrode for the other, and first andsecond electrode layers 20 and 21 are inorganic and/or solid.Non-exclusive examples of electrochromic electrode layers 20 and 21 arecathodically coloring thin films of oxides based on tungsten,molybdenum, niobium, titanium, lead and/or bismuth, or anodicallycoloring thin films of oxides, hydroxides and/or oxy-hydrides based onnickel, iridium, iron, chromium, cobalt and/or rhodium.

In one embodiment, first electrode layer 20 contains any one or more ofa number of different electrochromic materials, including metal oxides.Such metal oxides include tungsten oxide (WO₃), molybdenum oxide (MoO₃),niobium oxide (Nb₂O₅), titanium oxide (TiO₂), copper oxide (CuO),iridium oxide (Ir₂O₃), chromium oxide (Cr₂O₃), manganese oxide (Mn₂O₃),vanadium oxide (V₂O₃), nickel oxide (Ni₂O₃), cobalt oxide (Co₂O₃) andthe like. In some embodiments, the metal oxide is doped with one or moredopants such as lithium, sodium, potassium, molybdenum, vanadium,titanium, and/or other suitable metals or compounds containing metals.Mixed oxides (e.g., W—Mo oxide, W—V oxide) are also used in certainembodiments.

In some embodiments, tungsten oxide or doped tungsten oxide is used forfirst electrode layer 20. In one embodiment, first electrode layer 20 iselectrochromic and is made substantially of WO_(x), where “x” refers toan atomic ratio of oxygen to tungsten in the electrochromic layer, and xis between about 2.7 and 3.5. In certain embodiments, the electrochromicmixed metal oxide is crystalline, nanocrystalline, or amorphous. In someembodiments, the tungsten oxide is substantially nanocrystalline, withgrain sizes, on average, from about 5 nm to 50 nm (or from about 5 nm to20 nm), as characterized by transmission electron microscopy (TEM). Thetungsten oxide morphology may also be characterized as nanocrystallineusing x-ray diffraction (XRD); XRD. For example, nanocrystallineelectrochromic tungsten oxide may be characterized by the following XRDfeatures: a crystal size of about 10 to 100 nm (e.g., about 55 nm.Further, nanocrystalline tungsten oxide may exhibit limited long rangeorder, e.g., on the order of several (about 5 to 20) tungsten oxide unitcells.

The thickness of the first electrode layer 20 depends on theelectrochromic material selected for the electrochromic layer. In someembodiments, first electrode layer 20 is about 50 nm to 2,000 nm, orabout 100 nm to 700 nm. In some embodiments, the first electrode layer20 is about 250 nm to about 500 nm.

Second electrode layer 21 serves as the counter electrode to firstelectrode layer 20 and, like first electrode layer 20, second electrodelayer 21 may comprise electrochromic materials as well asnon-electrochromic materials. Non-exclusive examples of second electrodelayer 21 are cathodically coloring electrochromic thin films of oxidesbased on tungsten, molybdenum, niobium, titanium, lead and/or bismuth,anodically coloring electrochromic thin films of oxides, hydroxidesand/or oxy-hydrides based on nickel, iridium, iron, chromium, cobaltand/or rhodium, or non-electrochromic thin films, e.g., of oxides basedon vanadium and/or cerium as well as activated carbon. Also combinationsof such materials can be used as second electrode layer 21.

In some embodiments, second electrode layer 21 may comprise one or moreof a number of different materials that are capable of serving asreservoirs of ions when the electrochromic device is in the bleachedstate. During an electrochromic transition initiated by, e.g.,application of an appropriate electric potential, the counter electrodelayer transfers some or all of the ions it holds to the electrochromicfirst electrode layer 20, changing the electrochromic first electrodelayer 20 to the colored state.

In some embodiments, suitable materials for a counter electrodecomplementary to WO₃ include nickel oxide (NiO), nickel tungsten oxide(NiWO), nickel vanadium oxide, nickel chromium oxide, nickel aluminumoxide, nickel manganese oxide, nickel magnesium oxide, chromium oxide(Cr₂O₃), manganese oxide (MnO₂), and Prussian blue. Optically passivecounter electrodes comprise cerium titanium oxide (CeO₂—TiO₂), ceriumzirconium oxide (CeO₂—ZrO₂), nickel oxide (NiO), nickel-tungsten oxide(NiWO), vanadium oxide (V₂O₅), and mixtures of oxides (e.g., a mixtureof Ni₂O₃ and WO₃). Doped formulations of these oxides may also be used,with dopants including, e.g., tantalum and tungsten. Because firstelectrode layer 20 contains the ions used to produce the electrochromicphenomenon in the electrochromic material when the electrochromicmaterial is in the bleached state, the counter electrode preferably hashigh transmittance and a neutral color when it holds significantquantities of these ions.

In some embodiments, nickel-tungsten oxide (NiWO) is used in the counterelectrode layer. In certain embodiments, the amount of nickel present inthe nickel-tungsten oxide can be up to about 90% by weight of thenickel-tungsten oxide. In a specific embodiment, the mass ratio ofnickel to tungsten in the nickel-tungsten oxide is between about 4:6 and6:4 (e.g., about 1:1). In one embodiment, the NiWO is between about 15%(atomic) Ni and about 60% Ni; between about 10% W and about 40% W; andbetween about 30% O and about 75% O.

In some embodiments, the thickness of second electrode layer 21 is about50 nm about 650 nm. In some embodiments, the thickness of secondelectrode layer 21 is about 100 nm to about 400 nm, preferably in therange of about 200 nm to 300 nm.

Referring again to FIG. 1, substrates 24 and 25 have flat surfaces. Thatis, they have a surface coincides with the tangential plane in eachpoint. Although substrates with flat surfaces are typically employed forelectrochromic architectural windows and many other electrochromicdevices, it is contemplated that the multi-layer devices of the presentdisclosure may have a single or even a doubly curved surface. Stateddifferently, it is contemplated that each of the layers of stack 28 havea corresponding radius of curvature. See, for example, U.S. Pat. No.7,808,692 which is incorporated herein by reference in its entirety withrespect to the definition of single and doubly curved surfaces andmethods for the preparation thereof.

In one embodiment, ion conductor layer 10 is produced from a liquid ionconducting polymer feedstock that comprises a monomer, oligomer, ormixture of monomers and/or oligimers, a plasticizer, and an ionizablecharge carrier such as a lithium salt. Optionally, the ion conductingpolymer feedstock may additionally comprise a cross-linking catalystand/or a viscosity increasing agent. The ion conducting polymerfeedstock imparts certain mechanical and electrochemical properties toion conductor layer 10. The respective components of the ion conductingpolymer feedstock (i.e. monomer(s), oligomer(s), plasticizer(s),cross-linking catalyst(s), or viscosity-increasing agent(s)) may beoptimized to improve mechanical and/or electrochemical properties of theion conducting layer. For example, certain monomers may be selected tooptimize color, durability, and crosslink density while certainplasticizers may be selected to optimize ion mobility. The ionconducting polymer feedstock may also comprise other additives topromote device performance such as moisture reduction additives (e.g.nanoparticles of molecular sieves or fumed silica), UV stabilizers, pHbuffers, and the like.

Typical monomers, oligomers, or mixtures of monomers and/or oligomersused in the ion conducting polymer feedstock may comprise, for example,at least one functional group selected from the group of epoxy,hydroxyl, carbonyl, sulfonyl, ethylene, styrene, vinyl, isocyanate, andacrylate, or repeat units of siloxane, polysulfone, or an oligomercomprising one or more of the listed functional groups. The selectedmonomer or oligomer may be cyclic or, more preferably, aliphatic. Theselected monomer(s) or oligomer(s) may comprise monofunctional orpolyfunctional (e.g. difunctional or trifunctional) monomer repeatunit(s), i.e. a monomer repeat unit having one, two, three or morepolymerizable functional groups, or combination thereof, where thedegree of functionality and ratio of monofunctional to polyfunctionalmonomers may be tuned to optimize the mechanical, durability, andelectrochemical properties of ion conductor layer 10. For example, thedensity of the crosslink within ion conducting layer 10 tends toincrease with the amount and/or the degree of polyfunctional monomerpresent in the ion conducting polymer feedstock. By way of furtherexample, an ion conducting polymer feedstock having a ratio ofpolyfunctional monomer (e.g. diepoxide) to monofunctional monomer (e.g.monoepoxide) of about 3:1 would be expected to yield an ion conductinglayer having lower ion mobility and higher lap shear strength than anion conductor layer produced from a feedstock having a polyfunctionalmonomer to monofunctional monomer ratio of 1:1. Other variations in ionconducting polymer feedstock such as polymer backbone rigidity may alsoaffect the mechanical and electrochemical properties of ion conductinglayer 10.

Alternatively, a pre-formed polymer having crosslinkable functionality,such as glycidyl methacrylate (GMA) or poly-GMA, may be used in place ofthe monomer(s), oligomer(s), or mixture of monomer(s) and/or oligomer(s)in the ion conducting formulation. In one particular embodiment thepre-formed polymer may be polyethylene glycol methyl ether methacrylate(PEGMEMA) in combination with poly-GMA. The ratio of poly-EGMEMA topoly-GMA units in the pre-formed polymer may be in the range ofapproximately 1:1 to 9:1.

In some embodiments, the monomer(s), oligomer(s), or mixture ofmonomer(s) and/or oligomer(s) is/are present in the ion conductingpolymer feedstock in an amount ranging from about 0 wt. % to 90 wt. % ofthe of the total ion conducting polymer feedstock formulation. Forexample, in one embodiment, the monomer(s), oligomer(s), or mixture ofmonomer(s) and/or oligomer(s) is/are present in an amount ranging from 5wt. % to 50 wt. % of the of the total mass of ion conducting polymerfeedstock. By way of further example, in one embodiment the monomer(s),oligomer(s), or mixture of monomer(s) and/or oligomer(s) is/are presentat about 30 wt. % of the total mass of ion conducting polymer feedstock.

In any of these exemplary embodiments, the monomer(s), oligomer(s), ormixture of monomer(s) and/or oligomer(s) may preferably containpolyfunctional monomer in an amount ranging between about 0 wt. % andabout 25 wt. % of the total mass of ion conducting polymer feedstock,varied relative to monofunctional monomer to optimize mechanical andelectrochemical device properties. For example, ion conducting polymerfeedstock having difunctional and monofunctional monomer in a ratio ofabout 3:1 will produce an ion conducting layer having a highercross-link density than a feedstock having a 1:1 difunctional tomonofunctional monomer ratio. This higher cross-link density would beexpected to reduce ion mobility and may affect switching kineticsbetween less transmissive and more transmissive states. Additionally,higher cross-link density may also affect the adhesive and cohesiveproperties (as measured by lap shear tests) of the ion conducting layer.

The plasticizer of the ion conducting polymer feedstock may be any knownplasticizer for electrochromic or battery systems, such as sulfolane,3-methyl sulfolane, propylene carbonate, ethylene carbonate, orpolyethylene glycol dimethyl ether, optionally combined with aviscosity-increasing agent. In one embodiment, the plasticizer issulfolane, as ion conducting layers comprising sulfolane possessenhanced durability and color characteristics for the applicationsdescribed elsewhere in this application over those ion conducting layerscomprising propylene carbonate or polyethylene glycol dimethyl ether.

In some embodiments, plasticizer is present in the ion conductingpolymer feedstock in an amount ranging from 10 wt. % to 90 wt. % of theof the total ion conducting polymer feedstock formulation. For example,in one embodiment, plasticizer is present in the ion conducting polymerfeedstock in an amount ranging from 40 wt. % to 60 wt. % of the totalion conducting polymer feedstock formulation.

In some embodiments, the monomer(s), oligomer(s), or mixture ofmonomer(s) and/or oligomer(s) may be polymerized and cross-linked insitu where the polymerization reaction is initiated by a cross-linkingcatalyst comprising an ionizable charge carrier, preferably by cationicinitiation. The source of the ionic charge carrier may be selected froma lithium ion source, a sodium ion source, a potassium ion source, or aproton source. For example, in one embodiment, the source of theionizable charge carrier is lithium bis-trifluoromethanesulfonimide(LiTFSi). Optionally, one or more Lewis or BrOnsted acids, such as BF₃,trifilic acid, mesic acid, trifluoroacetic acid, and nanozeolites, maybe added to the liquid formulation where necessary or desired tocatalyze the polymerization reaction.

Alternatively, free standing fully formulated ion conducting films maybe used in place of the crosslinking ion conducting formulation or theliquid ion conducting formulation may be used in a “cast in place”process where a pre-formed cavity between the anode and cathode isproduced (edge sealed) and the formulation is forced into this cavitythrough fill ports.

In some embodiments, the ion conducting polymer feedstock comprises aviscosity-increasing agent. The viscosity-increasing agent may be anypolymer compatible with the polymerization system, whether or not thepolymer contains a reactive functional group. Suitable polymers include,for example, cellulose and cellulose derivatives (e.g. celluloseacetate, cellulose triacetate, cellulose propionate acetate, ethylcellulose, methylcellulose, etc.), polysulfones, and polymer esters. Incertain preferred embodiments, the durability of the ion conductinglayer may be improved where the viscosity-increasing agent lacks aminefunctionality and is substantially free of polyethylene glycol. In someembodiments, the coloring of the ion conducting layer may shift frommore yellow to less yellow or colorless where the viscosity-increasingagent is aliphatic and/or lacking amine functionality. In someembodiments, the viscosity increasing agent may be anhydrous to preventelectrolysis under the conditions of cycling. In some embodiments, theviscosity increasing agent may be solid and inert. Alternatively or inaddition to a polymer, the viscosity-increasing agent may comprise anaggregation of particles such as fumed silica.

In some embodiments, the ion conductor polymer feedstock may be storedfor a period of time prior to use in forming an ion conducting layer. Inone embodiment, the ion conducting polymer feedstock may be formulatedin two or more distinct components and stored in separate containers. Insuch an embodiment, for example, the first component may comprise amonomer, oligomer, or mixture of monomers and/or oligomers, the secondcomponent may comprise a cross-linking catalyst (i.e. an ionizablecharge carrier and/or acid), and either the first component or thesecond component or both may comprise other additives such as aplasticizer or viscosity-increasing agent. The separately-stored monomerand cross-linking catalyst components may be mixed at the point ofdeposition onto a substrate in proportions sufficient to result in thedesired cross-linking density upon polymerization.

In an alternative embodiment, the ion conducting polymer feedstock maybe formulated in a single container comprising monomer(s), oligomer(s),or mixture of monomer(s) and/or oligomer(s), a cross-linking catalyst,and other additives such as a plasticizer or viscosity-increasing agent.A single-container ion conducting feedstock may be used where themonomer and cross-linking catalyst components remain unreacted until anexternal energy source such as thermal or UV radiation is applied to thesystem to initiate polymerization and cross-linking.

The viscosity of the ion conducting formulation as dispensed may beengineered to achieve a desired viscosity. Regardless of the use ofsingle-container or multi-container feedstock, the ion conductingformulation as dispensed may, for example, have a viscosity of betweenabout 15,000 cP and about 100,000 cP at room temperature (i.e. 25° C.).By way of further example, in one embodiment the ion conductingformulation as dispensed may have a viscosity of between about 20,000 cPand 50,000 cP at room temperature. By way of further example, in oneembodiment the ion conducting formulation as dispensed may have aviscosity of between about 25,000 cP and 35,000 cP at room temperature.By way of further example, in one embodiment the ion conductingformulation as dispensed may have a viscosity of about 30,000 cP at roomtemperature.

In embodiments utilizing a multi-container ion conducting polymerfeedstock, each of the monomer component and the cross-linking catalystcomponent may be engineered to achieve a desired viscosity upon mixingof the two components for dispense (e.g. dispense from a nozzle onto asubstrate). In such embodiments, viscosity of the monomer component istypically increased by the addition of a viscosity-increasing agent tobe substantially higher than the desired dispense viscosity. Conversely,the viscosity of the cross-linking catalyst component is substantiallylower than the desired dispense viscosity. In one exemplary embodiment,a monomer component comprising an epoxy monomer may have a viscosity ofabout 40,000 cP at room temperature (i.e. 25° C.) and a cross-linkingcatalyst component may have a viscosity of about 5,000 cP at roomtemperature, where viscosity of the mixed monomer component and catalystcomponent as dispensed is between about 25,000 cP and about 35,000 cP,or more preferably about 30,000 cP, at room temperature.

The ion conducting layer incorporated into the multi-layer structures ofthe present disclosure may be prepared by a number of depositionprocesses including wet-coating, spray coating, dip coating, rollercoating, blade coating, screen printing, and nozzle application by asingle jet, multiple jets, or an array of nozzles.

Referring again to FIG. 1, ion conductor layer 10 may be incorporatedinto electrochromic multi-layer stack 28 by a series of steps involvingdispensing the ion conducing formulation then laminating and curing thestack. For example, ion conducting polymer feedstock is deposited ordispensed from a nozzle onto a first multi-layer stack comprising afirst substrate and a first electrode layer. A second multi-layer stackcomprising a second electrode layer and a second substrate issubsequently laminated onto the first multi-layer stack to form anelectrochromic multi-layer stack comprising, in succession, the firstsubstrate, the first electrode layer, the ion conducting formulationlayer, the second electrode layer, and the second substrate, the firstelectrode layer, the second electrode layer, or both comprising anelectrochromic material. Optionally, the first or second or both thefirst and second multi-layer stack(s) may comprise a polyisobutylene(PIB) seal around the edge forming a barrier between the environment andthe ion conducting formulation layer. The lamination step comprisesvacuum sealing of the first and second multi-layer stacks at 1 torr toremove air and press the ion conducting formulation layer to uniformthickness. The vacuum-sealed multi-layer stack may be heated to betweenabout 80° C. and about 150° C. to further seal the multi-layer stack,initiate polymerization and cross-linking, and melt polyisobutylene.Curing may occur by continuing to apply heat or other electromagneticradiation such as ultraviolet, infrared, or gamma radiation. Forexample, in one embodiment, curing may occur by application ofultraviolet radiation for about 5 seconds. In an alternative embodiment,curing may occur by application of heat for not less than 5 minutes. Incertain exemplary embodiments, curing may occur upon application of heator electromagnetic radiation for between 10 minutes and 2 hours, between15 minutes and 1 hour, or between 15 and 20 minutes. By way of furtherexample, curing may occur upon application of heat or electromagneticradiation over a period of hours or days. By way of further example,curing may occur upon application of heat or electromagnetic radiationover a period of hours or days. By way of further example, curing mayoccur upon application of heat or electromagnetic radiation for at least16 hours.

In accordance with one aspect of the present disclosure, anodicallycoloring electrochromic materials and/or cathodically coloringelectrochromic materials are prepared using thin-film depositiontechniques. The resulting anodic and cathodic electrochromic films havea range of desirable properties and characteristics. For example, in oneembodiment the anodic electrochromic material may have a bleached statevoltage value significantly greater than 2.0V. In another embodiment,the anodic electrochromic material is provided in an electrochemicallymatched state relative to a cathodic electrochromic material in itsfully bleached state for use in an electrochromic device. In anotherembodiment, the anodic electrochromic material is relatively stable; forexample, the lithium nickel oxide material does not darken from itsfully bleached state or deactivate (e.g., remain transparent but nolonger function as an electrochromic anode material or film) at elevatedtemperatures in the presence of ambient air.

In one embodiment, the electrochromic materials comprised by the anodeelectrode (i.e., the first or second electrode 20, 21; see FIG. 1) of amulti-layer structure of the present disclosure are inorganic ororganometallic and the electrochromic materials comprised by the cathode(i.e., the other of the first or second electrode 20, 21; see FIG. 1)are independently inorganic or organometallic. More specifically, theelectrochromic materials comprised by the anode and/or the cathode areinorganic or organometallic solid state materials with 3-D frameworkstructures comprising metals bridged or separated by anionic atoms ormolecules such as oxide, hydroxide, phosphate, cyanide, halide, thatfurther comprise mobile ions such as protons, lithium, sodium, potassiumthat can intercalate and de-intercalate as the material is reduced oroxidized during the electrochromic cycle.

The anodic and cathodic films incorporated into the multi-layerstructures of the present disclosure, except where specifically noted,may be prepared by a number of deposition processes including vapordeposition processes, wet-coating processes, spray coating processes,dip coating, and electrodeposition.

Having described the disclosure in detail, it will be apparent thatmodifications and variations are possible without departing the scope ofthe disclosure defined in the appended claims. Furthermore, it should beappreciated that all examples in the present disclosure are provided asnon-limiting examples.

EXAMPLES

The following non-limiting examples are provided to further illustratethe present disclosure. It should be appreciated by those of skill inthe art that the techniques disclosed in the examples that followrepresent approaches the inventors have found function well in thepractice of the disclosure, and thus can be considered to constituteexamples of modes for its practice. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments that are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the disclosure.

Example 1: Preparation of Ion Conducting Polymer Feedstock

A first mixture is prepared by combining 60 g of sulfolane, 40 g ofLiTFSi and 1 g of a BF₃ solution (10 mg BF₃.OEt₂ in sulfolane). A secondmixture is prepared by combining 60 g of sulfolane, 15 g of celluloseacetate (40K MW), 22.5 g of butyl glycidyl ether and 2.5 g of diglycidylcyclohexanedicarboxylate. The first mixture and second mixture arecombined immediately prior to dispense from a nozzle to form an ionconducting polymer feedstock having a viscosity of approximately 25,000cP at room temperature.

Example 2: Alternative Preparation of Ion Conducting Polymer Feedstock

A first mixture is prepared by combining 60 g of sulfolane, 40 g ofLiTFSi and 1 g of a BF₃ solution (10 mg BF₃.OEt₂ in sulfolane). A secondmixture is prepared by combining 60 g of sulfolane, 15 g of celluloseacetate (40K MW), 17.5 g of butyl glycidyl ether and 7.5 g of diglycidylcyclohexanedicarboxylate. The first mixture and second mixture arecombined immediately prior to dispense from a nozzle to form an ionconducting polymer feedstock having a viscosity of approximately 25,000cP at room temperature.

Example 3: Process for Assembling Multi-Layer Stack

As illustrated by FIG. 3, an edge seal B comprising polyisobutylene isdeposited on the perimeter of a first electrode A. The ion conductingpolymer feedstock C of Example 2 is coated onto first electrode B usinga slot die, a spray coater, a wire bar coater, or a roller coaterwithout contacting the edge seal B. A second electrode D is then pairedwith first electrode A supporting the ion conducting polymer feedstockand laminated to form multi-layer stack E. After lamination andapplication of a pressure between 5 and 50 psi, the ion conductingpolymer feedstock spreads evenly to cover the space between firstelectrode A and second electrode C. Edge seal B is compressed andbecomes directly adjacent to the ion conductor layer. The laminate iscured at 150° C. for 16 hours. Lap shear strength of the ion conductorlayer after cure is about 180 kPa, as measured at 1.27 mm at roomtemperature according to ASTM D3163.

What is claimed is:
 1. An electrochromic multi-layer stack, comprising:a first substrate and a second substrate, each having a transparentconductive layer on at least one surface; an electrochromic electrodeand an electrochromic counter electrode in contact with the transparentconductive layers; a cross-linked lithium-ion conducting polymer layerbetween the first electrochromic electrode and the electrochromiccounterelectrode; and wherein, at room temperature, the cross-linked ionconducting polymer is electrochemically stable at voltages between about1.3 V and about 4.4 V relative to lithium.
 2. The electrochromicmulti-layer stack of claim 1 wherein the cross-linked ion conductingpolymer has an electrochemical stability at voltages between about 1.3 Vand about 4.0 V relative to lithium.
 3. The electrochromic multi-layerstack of claim 1, wherein the cross-linked ion conducting polymer has anionic conductivity at room temperature of at least about 10⁻² S/cm. 4.The electrochromic multi-layer stack of claim 1, wherein thecross-linked ion conducting polymer has a lap shear strength in therange of about 200 kPa to 600 kPa.
 5. The electrochromic multi-layerstack of claim 1, wherein the cross-linked ion conducting polymer iselastically deformable and has an elongation to failure of at least 1mm.
 6. The electrochromic multi-layer stack of claim 1, wherein thecross-linked ion conducting polymer has a glass transition temperature(Tg) in the range of about −5° C. to about −40° C.
 7. The electrochromicmulti-layer stack of claim 1, wherein the first and second substratescomprise glass including a tempered carrier glass.
 8. The electrochromicmulti-layer stack of claim 1, wherein, at room temperature, thecross-linked ion conducting polymer has a lithium ion conductivity of atleast about 10⁻⁵ S/cm, has a lap shear strength of at least 100 kPa, asmeasured at 1.27 mm/min in accordance with ASTM International standardD1002 or D3163
 9. A process for manufacturing an electrochromicmulti-layer stack, the process comprising: (A) depositing an ionconducting polymer feedstock onto a first substrate comprising a firsttransparent conductive layer and a first electrode layer, (B) laminatinga second substrate comprising a second transparent conductive layer anda second electrode layer to the first substrate to form anelectrochromic multi-layer stack comprising, in succession, the firstsubstrate, the first transparent conductive layer, the first electrodelayer, the ion conducting polymer feedstock layer, the second electrodelayer, the second transparent conductive layer, and the secondsubstrate; and (C) irradiating the electrochromic multi-layer stack topolymerize the ion conducting polymer feedstock, forming a cross-linkedion conducting polymer layer, wherein the cross-linked ion conductingpolymer, at room temperature, is electrochemically stable at voltagesbetween about 1.3 V and about 4.4 V relative to lithium.
 10. The processof claim 9, wherein depositing the ion conducting polymer feedstockcomprises dispensing the ion conducting polymer feedstock from a nozzleat room temperature having a viscosity of about 20,000 cP to about50,000 cP.
 11. The process of claim 9, wherein forming a cross-linkedion conducting polymer comprises cross-linking the ion conductingpolymer to an extent to have a lap shear strength of at least about 200kPa.
 12. The process of claim 9, wherein forming a cross-linked ionconducting polymer comprises cross-linking the ion conducting polymer toan extent to be elastically deformable and still maintain mechanicalstrength.
 13. The process of claim 9, wherein forming a cross-linked ionconducting polymer comprises cross-linking the ion conducting polymer tohave an elongation to failure of at least 1 mm.
 14. The process of claim9, wherein the cross-linked ion conducting polymer, at room temperaturehas a lap shear strength of at least 100 kPa, as measured at 1.27 mm/minin accordance with ASTM International standard D1002 or D3163.
 15. Theprocess of claim 9, wherein the cross-linked ion conducting polymer, atroom temperature has a lithium ion conductivity of at least about 10⁻⁵S/cm.